Conventionally, there is proposed a light source apparatus for the replacement of a white light source such as an incandescent lamp, a fluorescent lamp or the like. The light source apparatus achieves a high color rendering property by using light emitting diodes emitting a red, a green, and a blue light and selecting a wavelength range of each light emitting diode in a specific range.
For example, there is disclosed a light source apparatus which has a red light emitter having a peak wavelength within the range from 600 nm to 660 nm, a green light emitter having a peak wavelength within the range from 530 nm to 570 nm, and a blue light emitter having a peak wavelength within the range from 420 nm to 470 nm, as shown in a table of FIG. 14 and a spectral power distribution depicted in FIG. 15 (see, e.g., Japanese Patent Application Publication No. 2007-173557).
In the above-mentioned examples, although melatonin suppressing efficiencies are low, there cannot be achieved a good color rendering property when lights emitted from the light emitters have sharp peak wavelengths. Furthermore, when any one of the peak wavelengths is deviated from the desired range in one or more light emitters, the color rendering property is deteriorated.
For example, as can be seen from FIG. 14, all of the peak wavelengths are within the above-mentioned ranges in the conventional examples 1 and 2 where the red light emitters thereof have a 620 nm peak wavelength and a 650 nm peak wavelength, respectively. However, the conventional example 2 has a color rendering index (Ra) lower than the conventional examples 1, in which Ra is a value indicating the color rendering property. It is thought because the conventional example 2 uses light emitters emitting light having a relatively sharp peak wavelength compared to the conventional example 1.
In case of the conventional example 1, a melatonin suppressing efficiency is high, though the color rendering property is good. In order to lower the melatonin suppressing efficiency, there can be considered a light source apparatus as shown in the conventional example 2 in which the peak wavelength of the red light emitter is 650 nm, which is shifted from the 620 nm peak wavelength of the red light emitter in the conventional example 1, as shown in FIGS. 14 and 15.
In the conventional example 2, however, a color rendering index (Ra) which is a measure of a color rendering property is lowered as shown in FIG. 14. As shown in the conventional examples 1 and 2, increasing the rendering effect and lowering the melatonin suppressing efficiency has a trade off relation, which is believed to be due to relatively sharp peak characteristics of the light emitters (FIG. 15) employed therein.